Pitch: 'Case Expressions' for Pattern-matching

[ASwiftUser]

I found it:

If not case

What is the recommended way of testing if a value does not correspond to an enumeration case with an associated value? Given the following declarations: enum Associated { case text(String) case number(Float) case flag(Bool) } let t = Associated.text("my text") Testing whether a value matches a specific case is readable (though awkward because of the implicit assignment): if case .text(_) = t { print ("found a text") } The opposite, testing whether a value does not match a sp…

This thread supports a not keyword that can be added to case. Thinking about it, Swift chose not to use keywords for Boolean operators and rather the symbols which makes me unsure if this is consistent with the current Swift syntax.